Cisco Firewall :: ASA 5510 ACL For Blocking Outbound SMTP
Jan 30, 2013
I'm trying to configure a simple ACL to block smtp traffic from leaving my LAN -- basically prevent internal users from setting up internet email accounts in their email clients and sending through that smtp server. i want my Exchange server only to send smtp traffic. here's what i have:
-access-list 102 extended permit tcp host 10.10.1.29 eq smtp any eq smtp <===10.10.1.29 is Exchange
-access-list 102 extended deny tcp any eq smtp any eq smtp
-access-list 102 extended permit ip any any
-access-group 102 in interface inside
after i apply this ACL to the ASA, i am still able to send from my internet email address setup in Outlook using my "foreign" smtp server.
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Aug 21, 2011
A recently added outbound rule has left my SMTP communications broken. I have since removed the rule, and had Cisco do some damage control, but it's still dropping some of the SMTP traffic. I get a number of NDR messages each day like the one below:Your message did not reach some or all of the intended recipients. Subject: RE: Christopher, Curt Sent: 8/19/2011 9:38 AM The following recipient(s) could not be reached:
[URL]
on 8/21/2011 9:49 AM
Could not deliver the message in the time limit specified. Please retry or contact your administrator.
<630.SM.Local #4.4.7>
Your message did not reach some or all of the intended recipients. Subject: RE: Christopher Curd Sent: 8/19/2011 9:38 AM The following recipient(s) could not be reached: JWillar@email.com on 8/21/2011 9:49 AM Could not deliver the message in the time limit specified. Please retry or contact your administrator. <630.SM.Local #4.4.7>
I've attached an image of my configuration (ASDM GUI). The part of the image highlighted in green are the SMTP rules. The part highlighted in yellow is another rule that I added about a month ago to block a SYN attack. This rule may be part of the problem because of the order it is in the list. Not sure, though.
I have had two Cisco techs Putty into my ASA to check things out. I think they've done all they can. I wonder at this point if it be wise to just reload the last good running-config I have prior to the Outbound rule being added.
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Nov 26, 2012
I am attempting to block outbound traffic for a specific PC on my LAN using the ASDM.
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Mar 30, 2011
Below is the interesting part of my config. I have static NAT configured and working inbound for the Exchange Server and the Barracuda, however outbound traffic from those hosts comes out as the interface IP. Thoughts? I've tried a number of things (outside, inside), etc.
object network obj_any
subnet 0.0.0.0 0.0.0.0
object network DSN-EXCH01
host 10.250.231.51
object network MAIL-IN
host 10.250.231.50(code)
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Oct 14, 2012
I have a LAN with several linux boxes (Fedora 17, both 32 and 64 bits), as well a a WInXP box. All of these are connected to the same switch, which is connected to the inside port of my PIX 515.
For a few sites (mozilla.org happens to be one of them), for http access, the tcp connection is established, but the "GET" request - or anything else for that matter - will not go through the PIX (from inside to wan). I have verified this by first, using wireshark to watch the packets being sent out from the client box, then by using the trace function in the PIX to see that the packets ARE arriving at the inside interface, but ARE NOT sent out of the wan interface.
This is for the linux boxes ONLY. When I do the same thing with my WinXP box, all works: in the PIX trace, I see the packets arrive at the inside interface, and leave the wan interace. And access to these sites are okay.
(What's a bit weird, although somewhat expected, when I connect my android phone to my LAN via WiFi, it too is unable to reach those sites - but then again, android is linux, right?)
In addition to the tracing, I have narrowed this problem down by connecting a linux box directly to my DSL router, then replacing the PIX with a simple router/gateway. Both of those solutions work.
Some background:
I have been using this PIX for about 10 years now, with the same configuration (except IP addresses). Only in the last several months has this problem started to show up.
I got this pix from a dead company at a really great price (free), so I'd like to keep it, and not have to spend money on something else. I don't have any support license, and have not been able to get any software upgrades. Here is its version info:
taz(config)# sho ver
Cisco PIX Firewall Version 6.2(2)
Cisco PIX Device Manager Version 2.0(2)
Compiled on Fri 07-Jun-02 17:49 by (code)
Serial Number: 405200362 (0x1826ddea)
Running Activation Key: 0x38ac31f3 0x0630df47 0x9a77b805 0x8bc39a60
PS: Since this PIX is at its end of life, I was wondering if any of the software upgrades would be now available without a license?
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Jun 20, 2011
I have a XP workstation behind my ASA that can not connect to a client's network via Cisco VPN Client using IPSec...
In the logs it shows the translation is working on 500 but the VPN Client has the error 412, that the client is not responding.
Config below
ASA Version 8.2(1)!hostname RWFW1enable password encryptedpasswd encryptednames!interface Vlan1nameif insidesecurity-level 100ip address 192.168.1.1 255.255.255.0!interface Vlan2nameif outsidesecurity-level 0ip address x.x.x.x
[Code].....
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Feb 20, 2009
I've purchased a WRT310N router to replace an existing wired router, and am in the process of setting up the outbound firewall rules. While I see settings to restrict access to all sites (or specific sites) for a specific protocol, I don't see an easy way to only allow access to one specific site.I want to restrict outbound SMTP to one server (my ISP's).
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Mar 21, 2013
I have a ASA 5510 (ver 8.4) and I have been all over the support sites looking for what I am doing wrong. I have a sanitized cut n paste of the OBJECT, NAT, ACCESS-LIST and Packet Tracer output and it keeps failing on the NAT with a rpf-check. Once i get the SMTP flowing I have to open up HTTP and HTTPS to one of the servers also.
Here it is:
RVGW# sh run object
object network WiFi
subnet 172.17.100.0 255.255.255.0
[Code]......
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Jan 30, 2012
I know I can use the RTR statement to determine when the primary ISP circuit goes down via this technote: url...My question can I assign static Nats on the backup ISP connection to the same inside servers in the dmz.?Example 10.1.1.11 is mapped to ISP1 ExternaIP of 65.217.77.11. Can it 10.1.1.11 also be mapped to ISP2's 208.217.77.11?This way I can get my DNS changed and my inbound traffic to servers in my DMZ on the asa 5510 running 8.0.3 code can continue to receive Inbound traffic.
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Jan 24, 2012
I have the need to do an outbound NAT redirection. So what I mean is this. I have a custom program that uses SSH to port 22 from a server inside the ASA firewall. This goes out to a server on the Internet over port 22. The ISP of the SSH server told me that they changed their SSH port from 22 to 2102. So instead of changing the custom code on the developed application on the server... I thought it would be easier to do a OUTBOUND NAT redirection for the ASA to see port 22 from the server and redirect it OUTBOUND to port 2102.
so for example:
The server is at 192.168.0.2 and it uses a program to initiate SSH traffic to 205.246.1.1. The server sends to port 22 but I need it automatically changed on the firewall to port 2201 at 205.246.1.1.
It is a Cisco ASA 5510. The server at 192.168.0.2 does have a fixed IP address on the outside with INBOUND NAT for things like port 25 (mail) traffic etc. Lets pretend that was at 64.18.23.60.
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Nov 20, 2011
I'm running a Cisco ASA 5510 with version 7.2(3) and I've been tasked with permitting some inbound & outbound TCP & UDP ports to/from a specified address space on the internet.
In looking at my current ASA config I see other access lists already configured so I'm assuming I can just set up a new access list in similar fashion, but I wanted to verify here first.
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Oct 11, 2012
I have an issue with my mail server(SME Server) which is behind a Cisco ASA 5500(firewall) problem is that if one leaves my network they can receive but can not send email via my SMTP also internal people can only send if they use the IP address of the server rather than the domain [URL]
here is my layout
ISP - ASA 5510 - LAN (includes mailserver)
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Nov 28, 2012
We have hosted spam filter service with 3rd party vendor. My vendor is switching to different spamming services and I need to add ip address lets say 44.33.454.32 to the list of allowed system that can connect to my smtp service. I am going over my firewall 5510 configs and I think I need add the entry like this: “access-list outside-to-inside extended permit tcp object-group obj-44.33.454.32 interface outside eq smtp”. [code]
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Dec 6, 2012
We have a ASA5510 and I need to open port 22 for a speacific IP in our LAN outbound only.
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Oct 25, 2012
We have a 5510 (8.2) with the following 4 interfaces (security-levels) inside (95), outside(0), dmz(25), and test (95). The dmz network is 10.10.10.0/24 and the outside interface is 40.133.84.69.We have run into a situation where a dmz hosted iRedMail server running postfix (10.10.10.51) is relaying mail which in some cases points back to us at 40.133.84.69 and into our Exchange server. In these cases in the dmz server's mail logs we see postfix timeout trying to connect to smtp at 40.133.84.69. When I try to telnet from 10.10.10.51 to the outside interface on port 25 it times out.We've tried different ways to allow the outside adapter to permit smtp (or any service!) from 10.10.10.51 but we're left scratching out heads.
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Mar 5, 2012
how to go about setting up the ASA to block any SMTP traffic outbound except for our Exchange Server. This is in relationship to a SpamBot issue that blacklisted us. I have an ASA 5510 running version 6.2(5) / 8.2(2) with three ports. DMZ, Inside and the Outside interface. Up till today, I only needed to block outside traffic to our internal network which I used the ASDM to configure a rule on the outside interface for an incoming rule. I am assuming I need to create an outgoing rule on the outside interface; however, just to make sure I understand the terminology/traffic flow, I created the rule with my computer as the source (192.168.0.131) with ALL destination and the service as HTTP. My logic, which seems to fail here, is that any traffic from my computer going outbound would be blocked; however I am still able to browse... That said, if I were to change the source as the Exchange server and the Service Type to SMTP, it would not actually block traffic and therefore not solve our problem. I even gone as far as permitting traffic from my computer, expanding the hit counter and I see no hits. So I am no doubt doing this wrong. What I do know, is when I first created the rule, a second rule was automatically created (Implicit rule) that deny all sources and blocked all HTTP traffic until I changed it to Permit?
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Nov 30, 2011
I have an ASA 5510 running version 7.0. I have a problem with an exchange server using a static map and its outbounc connectivity. It connects outbound through the global address even though inbound connectivity works fine through the static mapping. The recent changes are changing of the zero route through a different interface (there are to circuit connected to this ASA on different interfaces). So the idea was to get all workstations in the office using the global address and routing out through one circuit, and the servers connecting in/out through the other circuit. Shouldn't a static mapping ignore what the zero route is?
Here are what I believe to be the relevant configs.
interface Ethernet0/0
description New 6mb circuit
speed 100
[Code]....
So exchang2 server can be connected to from the outside properly via IP xxx.207.51.231/exchange2-outside, but all outbound connections from this server are going out via IP xxx.122.47.218/circuit-6mb as do all the workstations due to the global address statement.
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Jul 30, 2012
I have an ASA 5510, one public IP address on my outside interface, an internal email server and a private network.I would like...
1: Users on my private network to be able to access the internet (PAT them to external outside address)
2: Email to be delivered to my MX (my single public IP address translated back to my internal email server.
i.e. can I share my single public IP address to serve translation in both directions (private users surfing the Internet (in-to-out) and an outside to inside NAT for email) ?
Email (MX) = 1.2.3.4
Public (outside) address = 1.2.3.4
Email server internal = 10.1.2.3
Internal private subnet for users = 10.0.0.0/8
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Jun 3, 2012
In Cisco ASA 5510 , outlook port only permit ( pop3 995/smtp :587) with TLS encryption. How we can do it thru ASDM .
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Jun 27, 2011
I have recently setup Splunk to receive my syslog messages from my ASA 5510. In the past I used kiwi without observing this issue, but I needed more features than kiwi had available. Anyway, anytime I stop the splunk service my asa does not allow any outbound connections to be established.
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Jun 11, 2012
We have configured ASA 5510. We have configure Ethernet 0/0 ( Outside ) connected with ADSL line and Ethernet 0/1 ( Inside ) Local LAN. we have configured NAT and all the traffic is passing through outside interface. Now we have connected ethernet 0/3 ( leasedline ) interface with static public IP. Now we want to allow SMTP traffic to pass through from this interface.
How to configure it if we want our local lan SMTP traffic sending through new leased line ( Static Public IP ).
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May 10, 2011
I have cisco ASA 5510 with ios version 7.07 & all users are browsing the internet via PAT through ASA. i want to block some sites/URLs like facebook, yahoo etc.
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Dec 13, 2010
I have a Cisco ASA 5510. I have detected an infected workstation on my internal LAN which has caused my IP to be blacklisted by Barracuda Networks and other RBL. I have scanned and cleaned the workstation removing the spambot. I want to prevent all my internal workstations from sending SMTP traffic on Port 25 through my ASA 5510 device. I only need to allow my Exchange Server access to send out traffic on port 25. configure this setup using ASDM 5.0? I know it may be easier using CLI, but using the ASDM would really be preferred.
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Nov 16, 2011
How to block a single website, but I want to do the opposite. I would like to block all website except for a handful of them. Any example configs?
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Sep 10, 2012
We have a Cisco ASA 5510 with a CSC SSM 20 module installed. As of this morning a valid site (Public School System) is being blocked at my site. It says the site is of High risk. I have tried entering the site in the block list exceptions but it still comes up as a high risk site.
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Jul 8, 2012
We have a Cisco ASA 5510 with a CSC SSM 20 module installed. As of this morning a valid site (Public School System) is being blocked at my site. It says the site is of High risk. I have tried entering the site in the block list exceptions but it still comes up as a high risk site...
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Dec 20, 2012
I have an ASA 5510 deployed and we are getting a tonne of port scanning traffic (who isn't these days) and ping traffic.The threat scanning thresholds seem a bit too high and was wondering if there is a way to use a Service Policy Rule to perform a Shun/Block of the hosts rather than the firewall simply blocking the request via the ACL and sending a reply.
In other words, if I do nothing, I know the ACL is protecting the resources but it is still replying to the client connection. I want the end result to be the same as a "Shun" where the connection is dropped and no reply is sent. how to employ Service Policy Rules to thwart Port Scanning and/or IP Spoofing?
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Oct 11, 2011
I've got some problem with my Mail Server since I've migrated to an ASA5510.Actually the server is in a DMZ with a private Ip ( 10.x.x.2) and it is translated to a Public IP ( 194.x.x.65).I use these configuration :
static (DMZ,LAN) 194.x.x.65 10.x.x.2 netmask 255.255.255.255 static (DMZ,LAN) 194.x.x.66 10.x.x.3 netmask 255.255.255.255 static (DMZ,WAN) 194.x.x.65 10.x.x.2 netmask 255.255.255.255 static (DMZ,WAN) 194.x.x.66 10.x.x.3 netmask 255.255.255.255 static (LAN,DMZ) 192.168.0.0 192.168.0.0 netmask 255.255.248.0
Some Users received in there mailbox a system administer error message :
Object : Impossible to deliver : test Your message could not be deliver to one or more of its recipients: 421 SMTP connection went away!
When they try to re sent it some times later, message is sent without problem.
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Aug 2, 2011
We had a problem with SMTP inspection dropping some regular emails (Cisco 2901 IOS 15.0). The original configuration.
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Jun 21, 2011
We had a problem with SMTP inspection dropping some regular emails (Cisco 2901 IOS 15.0).Incoming mails are going thru Spam and Virus Blocker so that bypassing SMTP inspection is not security issue in this case.
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Mar 14, 2013
IOS Firewall (ZBF) Limit SMTP connections from same IP
we are running a Postfix MTA behind a IOS Firewall (ZBF) on a CISCO1921. Sometimes we get more than 2000 smtp login attemps like
postfix/smtpd[123456]: connect from (...) (...) postfix/smtpd[123456]: lost connection after AUTH from (...)
in one second. May be bruteforce or DoS ... nevertheless - we like to protect the Postfix MTA from this stuff.
Can we inspect the smtp and limit connections in a time period from the the same IP? Something like "not more than 10 smtp connections during 60 seconds from the same ip" .
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Oct 5, 2011
I'm having some issues getting ActiveFTP to pass through an ASA 5505, I finally found out when I tested the FTP via cmd on windows(after the major hassle of getting credentials out of the software co) that it does open the connection on the control port, but whenever I try to send/recieve data the connection is dropped, for troubleshooting purposes I've even gone as far as opening up all ports 1-65535 with an acl to no avail, I believe the FTP traffic is encrypted with SSL(can't get a solid Y/N from the company).
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Mar 5, 2012
I have an ASA 5500 Firewall. I need to figure out how to log all events using Port 25 to determine if there are any rogue devices on our network. I was trying to figure out how to do this via the Real-Time Monitoring (filter) but have had no success.
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